Methods for producing composite nanoparticles

ABSTRACT

Size-confined nanocomposite powders and methods for their manufacture are provided by coating fine powders with a nanoscale powder of a different composition. The nanocomposite plastics disclosed offer performance characteristics approaching those of metals and alloys. The nanocomposite powders are alternatively used for dispersion strengthening of metals, alloys, and ceramics. Novel materials based nanotechnology for energy devices and programmable drug delivery are disclosed.

RELATED APPLICATIONS

The present invention claims priority to U.S. Provisional ApplicationNo. 60/357,946 filed on Feb. 19, 2002 entitled “POST-PROCESSED PARTICLESAND RELATED NANOTECHNOLOGY FOR SIGNIFICANTLY IMPROVED MATERIALPERFORMANCE”, the specification of which is incorporated herein byreference in its entirety. The present invention is also acontinuation-in-part of co-owned U.S. patent application Ser. No.10/004,387 entitled “NANO-DISPERSED POWDERS AND METHODS FOR THEIRMANUFACTURE” filed on Dec. 4, 2001, now U.S. Pat. No. 6,652,967 which isincorporated herein by reference in its entirety, and which claimspriority to provisional application No. 60/310,967 filed Aug. 8, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to use of nanotechnology,and, more particularly, methods to produce significantly improvedmaterial performance through the use of composite nanoparticles.

2. Relevant Background

Powders are used in numerous applications. They are the building blocksof electronic, telecommunication, electrical, magnetic, structural,optical, biomedical, chemical, thermal, and consumer goods. On-goingmarket demands for smaller, faster, superior and more portable productshave demanded miniaturization of numerous devices. This, in turn,demands miniaturization of the building blocks, i.e. the powders.Sub-micron and nano-engineered (or nanoscale, nanosize, ultrafine)powders, with a size 10 to 100 times smaller than conventional micronsize powders, enable quality improvement and differentiation of productcharacteristics at scales currently unachievable by commerciallyavailable micron-sized powders.

Nanopowders in particular and sub-micron powders in general are a novelfamily of materials whose distinguishing feature is that their domainsize is so small that size confinement effects become a significantdeterminant of the materials' performance. Such confinement effects can,therefore, lead to a wide range of commercially important properties.Nanopowders, therefore, are an extraordinary opportunity for design,development and commercialization of a wide range of devices andproducts for various applications. Furthermore, since they represent awhole new family of material precursors where conventional coarse-grainphysiochemical mechanisms are not applicable, these materials offerunique combination of properties that can enable novel andmultifunctional components of unmatched performance. Yadav et al. in aco-pending and commonly assigned U.S. patent application Ser. No.09/638,977 which along with the references contained therein are herebyincorporated by reference in full, teach some applications of sub-micronand nanoscale powders.

It has been anticipated by those skilled in the art that sizeconfinement could potentially produce materials with significantlyimproved strength, toughness, hardness, and other mechanical properties.However, size confinement has been difficult to reduce to commercialpractice. The reasons for this failure, in part, include (a) currentinability to retain the nanoscale grain size when nanoparticles arepost-processed into a final commercial product, and (b) agglomerationand aggregation of nanoparticles that in turn produces defects and poorbonding at interfaces.

Yet another method of improving the mechanical performance of materialsthat is known to those in the art is to employ particles to dispersionstrengthen materials. Dispersion strengthening is a method used toincrease the strength and high temperature performance of metal alloysby incorporating a fine distribution of hard particulates within aload-bearing matrix. These materials are formed, for example, by mixingparticles with a matrix material comprising the metal, metal alloy, orother material to be strengthened. This method takes advantage of thefact that dislocation motion is hindered by the presence of the fineparticulate. It is expected that as nanoparticles replace microparticlesin dispersion-strengthened materials, the performance of these materialswill increase.

However, it has been difficult to use nanoscale particulates incommercial dispersion strengthening applications because of poor bondingat the matrix and the nanoparticle dispersant interface. The lack of anintimate, uniform bonding between the matrix and dispersant materialsresults in sub-optimal performance of the composite materials. Further,conventional techniques experience difficulty in achieving andmaintaining a homogeneous distribution of the nanoparticles in thematrix.

In general, the commercial promise and social benefits of nanotechnologyare currently limited by the difficulty in post-processing nanoparticlesinto nanotechnology products. There is a need for a technology that canaddress these post-processing limitations.

SUMMARY OF THE INVENTION

Briefly stated, the present invention involves the use of nanotechnologyto produce composite nanoparticles, as well as new classes of materialsfrom those composite nanoparticles. The invention addresses known issueswith the use of nanoparticles and offers unusual methods for makingnovel materials useful in a wide range of applications. Morespecifically, the invention teaches method to create materials fromplastics that can compete with metals and alloys in certainapplications. The invention further teaches method to create materialsfrom resins, ceramics, metals or alloys that are expected todramatically improve the performance of the constituent materials theyare fabricated from. Further, the invention discloses some illustrativeapplications and their commercial significance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary overall approach for producing unusualmaterials in accordance with the present invention; and

FIG. 2 shows an exemplary overall approach for producing a product fromthe unusual materials in accordance with the present invention;

FIG. 3 illustrates and example of nanocomposite particle production; and

FIG. 4 illustrates production of useful materials from nanocompositepowders in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is generally directed to size-confined, interface-fusednanocomposite particles and products produced from such particles.Composite nanoparticles produced in accordance with the presentinvention comprise, for example fine powders in which nanoscaleparticles are bonded to the surfaces of nanoscale or micron scaleparticles of a matrix material. An important difference between othermethods that merely teach coating of a powder with another substance, isthat in present invention the nanoscale particles on the surface and thecoated powder chemically bond and form a layer where the twocompositions create a state synergistically reducing the free energiesfrom the bonding. Thus, the coated nanocomposite particles taught hereinare characterized by the composition of the powder coated, compositionof the nanoparticles that form the coating, and the distinct compositionof an interface that results from the bonding process and consequentreduction in the chemical potential. Therefore, unlike other techniquesin the art that merely teach methods for forming coated powders, thisinvention teaches a novel composition of matter. Also, unlike priorapproaches for forming composites materials, the present inventionenables a high degree of control and flexibility in engineering theinterface between the nanoparticle dispersant and the matrix material.Further, the resulting powder is uniform at a fine powder scale to thatwhen the composite nanopowders are used to form materials, uniformityand homogeneity of the resulting material is readily controlled.

Definitions

For purposes of clarity the following definitions are provided to aidunderstanding of description and specific examples provided herein:

“Fine powders”, as the term used herein, are powders that simultaneouslysatisfy the following:

-   -   1. particles with mean size less than 100 microns, preferably        less than 10 microns, and    -   2. particles with aspect ratio between 1 and 1,000,000.

“Submicron powders”, as the term used herein, are fine powders thatsimultaneously satisfy the following:

-   -   1. particles with mean size less than 1 micron, and    -   2. particles with aspect ratio between 1 and 1,000,000.

“Nanopowders” (or “nanosize powders” or “nanoscale powders” or“nanoparticles”), as the term used herein, are fine powders thatsimultaneously satisfy the following:

-   -   1. particles with mean size less than 250 nanometers, preferably        less than 100 nanometers, and    -   2. particles with aspect ratio between 1 and 1,000,000.

“Pure powders,” as the term used herein, are powders that havecomposition purity of at least 99.9%, preferably 99.99% by metal basis.

“Powder”, as the term used herein encompasses oxides, carbides,nitrides, chalcogenides, metals, alloys, and combinations thereof. Theterm includes hollow, dense, porous, semi-porous, coated, uncoated,layered, laminated, simple, complex, dendritic, inorganic, organic,elemental, non-elemental, composite, doped, undoped, spherical,non-spherical, surface functionalized, surface non-functionalized,stoichiometric, and non-stoichiometric form or substance.

The present invention involves size confinement, and in particularinvolves size confinement through the use of nanoscale particles.

One feature of the present invention involves forming nanocompositeparticles (also called nanocomposite powders) that are size-confined inthat they retain useful properties associated with size confinement whenplaced in proximity with other matter as required by most usefulapplications.

It is known that the mechanical properties of materials can be improvedby dispersion strengthening or hard working the materials to introduceinterfaces where dislocations get pinned. The emergence ofnanotechnology has led those in the art to theoretically suggest thatmaterials having nanoscale dimensions could be used to form unusuallysuperior performing materials, superior in strength, modulus, creep andother commercially useful characteristics. Despite the potentialoutlined by theory, in practice this has not been reduced to commercialuse. In part, this failure is because it is very difficult to retain thenanoscale dimensions as nanoparticles are processed into final usefulproducts. When used as dispersants, it is difficult to disperse thenanoparticles homogeneously in a matrix. Further, it is difficult toprocess the nanoparticles and a matrix to achieve intimate bonding atthe interface; normally, defects or the presence of gases adsorbed ontothe interfaces causes the bonding to be poor.

Conventional methods of forming a product from nanoparticles or forminga nano-dispersion strengthened material combines the process of formingthe end product and interface engineering. That is, both the productmanufacturing step and the interface-engineering step happen together,each affecting and often creating confounding interactions with theother. To be more specific, numerous products prepared from powdersrequire sintering which normally is practiced at elevated temperatures.These elevated temperatures, unfortunately, also cause grain coarseningand the loss of nanoscale confinement. Similarly, dispersion ofparticulates in alloys is often done at elevated temperatures or inmolten form of a metal or alloy. These processing conditions lead tophase segregation or poor distribution and bubbling out of the particlesgiven that they have gases adsorbed at their interface.

It is also common to prepare mixtures of powders in advance of themanufacturing processes used to make a useful article. The preparedmixtures are packaged, stored, and handled in ways that affect theintegrity of the powders. For example, separation of the mixture reduceshomogeneity leading to variability in performance of the material in themanufacturing processes.

In accordance with the present invention, the product manufacturingoperation(s) and the interface-engineering operation(s) are separated.The interface engineering is done first in operations shown in FIG. 1,and at processing conditions that prevent or limit the loss of sizeconfinement effects. Next, the product manufacturing operations shown inFIG. 2 are conducted. Preferably, the nanocomposite powders produced inthe interface engineering phase are suitably rugged to preserve sizeconfinement effects during portions of the manufacturing operationsshown in FIG. 2 in which size confinement effects are relevant, as wellas any packaging, storage, and handling operations that occur betweenthe interface engineering operations shown in FIG. 1 and themanufacturing operations shown in FIG. 2.

As shown in FIG. 1, matrix powders comprising fine powders of acomposition suitable for the desired matrix are selected in 101, wherethe fine powders may be nanoscale, micron scale, or in some caseslarger. In 103, nanoscale powders of a second composition, differentthan the matrix material selected in 101, are selected. The compositionof the material selected in 103 is selected to be suitable as a filleror dispersant in the desired composite.

In one embodiment, the nanoscale powders or submicron powders selectedin 101 are coated in operation 105 with the powders selected in 103,preferably such that coating is significantly thinner than the compositepowder size. On weight basis, it is preferred that the loading of coatednanoparticulate material be less than or equal to 40% by weight of theresultant nanocomposite powder, and more preferred to be less than 5% insome applications. In some applications, this loading can be as small as0.25% to 2%, or lower than 0.25%, and in others it may be higher than40% by weight. This coating can be done using techniques such aschemical vapor deposition, physical vapor deposition, monolayer reactivedeposition, precipitation, condensation, selective and controlledreaction, infiltration, laser deposition, and those taught by commonlyowned co-pending U.S. patent application Ser. No. 10/004,387 filed onDec. 4, 2001 entitled “NANO-DISPERSED POWDERS AND METHODS FOR THEIRMANUFACTURE”, the specification of which is incorporated herein byreference. The particles so produced can subsequently be processed intouseful products. The presence of the coating prevents or limits thecoarsening of the nanoparticles and the coated powder, and gives themanufacture greater control over the manner in which size confinementeffects of the composite particles affect the properties of the usefularticle being produced.

In another embodiment, fine powders or submicron powders or nanoscalepowders of first composition of material (selected in operation 101) arepost-processed in operation 105 with nanoparticles of second compositionselected in operation 103. The post-processing produces compositeparticles where the nanoparticles of second composition coat the powdersof first composition. The coating bonds the interface between the firstand the second composition. The coating performed in 105 can becomplete, partial, dense, porous, monolayer, multi-layer, uniform ornon-uniform. The composite particles so produced can then be collectedin operation 107, and processed into useful products as suggested inFIG. 2.

The presence of the coating and interface bonding (a) prevents or limitsthe coarsening of the nanoparticles, and (b) helps retain the sizeconfinement of the powders of first composition due the presence of thecoating of second composition. For this embodiment, one or more of thesemethods can be employed to form the composite particles—cryogenicfusion, mechano-chemical fusion caused by various variations of milling,chemical vapor deposition, physical vapor deposition, reactivedeposition, precipitation, condensation, selective and controlledreaction of surface, infiltration, laser deposition, and those taught bya commonly-pending U.S. patent application Ser. No. 10/004,387.

Examples of a first composition selected in 103 in a composite particlecan be a polymer, metal, ceramic, alloy or a composite. The secondcomposition can also be a polymer, metal, ceramic, alloy or a composite;however, for this invention the substance constituting the firstcomposition is different in one or more way than the second composition.

Some non-limiting illustrations of a polymer useful as a firstcomposition in 103 include polyethylene, polypropylene, polystyrene,polyurethane, polyacrylates, polycarbonates, polyamides, polyamines,polyimines, and any other carbon containing polymeric compound.

Some non-limiting illustrations of a ceramic useful as a firstcomposition in 103 include oxides, carbides, nitrides, borides,chalcogenides, halides, silicides, and phosphides. Ceramics for thisinvention can be single metal compounds or multi-metal compounds. Thecomposition selected in 103 may also comprise complex compositions suchas oxycarbides, oxynitrides, carbonitrides, boro-nitrides, andnon-stoichiometric compositions.

Some non-limiting illustrations of a metal useful in as a firstcomposition in 103 include transition metals, alkali metals, alkalineearth metals, rare earth metals, and semi-metals. It is preferred thatthe metal be low cost and otherwise compatible with the processing andintended use for the metal. Some of the preferred metals for dispersionstrengthening include those comprising copper, molybdenum, iron, nickel,and cobalt.

Some non-limiting illustrations of an alloy that can be prepared usingthe nanocomposite powders in accordance with this invention includealloys comprising two metals, alloys comprising three or more metals,alloys comprising metals and semimetal or nonmetal or both. Some of thepreferred alloys for dispersion strengthening include those comprisingsteel, iron alloys, aluminum alloys, brass, bronze, nickel alloys,molybdenum alloys, titanium alloys, superalloys, and alloys comprisingof rare earth elements.

Fine powders, submicron powders, and nanoparticles for this inventionmay be produced and processed by any method including those that havebeen discussed in commonly owned patents (U.S. Pat. Nos. 6,344,271,6,228,904, 6,202,471, 5,984,997, 5,952,040, 5,905,000, 5,851,507, and5,788,738) which along with the references cited therein areincorporated herein by reference.

The manufacturing processes shown in FIG. 2 generally involve producing,selecting or otherwise obtaining size-confined nanocomposite powders inoperation 201, such as described in reference to FIG. 1. Optionally, thenanocomposite powders may be post-processed to simplify partmanufacturing in 203. Post-processing operation 203 may involve any of avariety of processes such as thermal treatment, drying, chemicaltreatment, surface modification, de-agglomeration, agglomeration,reduction, oxidation, dispersion, static removal, and the like that havean impact on handling the nanocomposite powder during manufacture, oralter the nanocomposite powder's performance in the manufacturedproduct. In operation 203, a finished or partially finished part ismanufactured from the size-confined nanocomposite powder usingtechniques including injection molding, spray coating, pressing,hipping, tape casting, screen printing, mold stamping, ink-jet printing,melt processing, electrophoresis, and the like.

FIG. 3 and FIG. 4 illustrate the nanocomposite production andmanufactured product production processes described in FIG. 1 and FIG.2. As generally shown in FIG. 3, fine powder particles 301, selected inoperation 101, are processed with nanoscale powders 303, selected inoperation 103, to form a nanocomposite 305. FIG. 3 illustrates anexample nanocomposite particle 305 in cross-section in which thenanoparticles 303 substantially completely bond with the surface of finepowder particle 301. However, as noted earlier, the surface coveragedegree and uniformity are a matter of design choice. Significantly,nanoparticles 303 form an energy favored bond with the surface of finepowder particle 301 so that, absent application of external energy,particles 303 will remain bonded with the particle 301.

In FIG. 4, once the nanocomposite powders 401 are selected in step 201,they may be post-processed (not shown), and formed into a consolidatedstructure 405 by various manufacturing means. The consolidated structure405 may be formed in a manner that retains the surface bonding ofnanoparticles 303 and fine powder particles 301. Alternatively, themanufacturing process may provide sufficient energy to break some or allof the bonds.

EXAMPLE 1 Dispersion Strengthening of Materials

Dispersion strengthening is a method to increase the strength of metalalloys by incorporating a fine distribution of hard particulates. Thismethod takes advantage of the fact that dislocation motion is hinderedby the presence of the fine particulate. This can be quantified by thefollowing equation:π=Gb/λwhere τ=stress to force a dislocation through the particulate, G=shearmodulus, b=Burger's vector, λ=spacing between particulate.

One of the primary variables in this equation (for a given chemistry) isthe spacing between the particulate. This spacing can be reduced bydecreasing the size of the particulate, giving a resultant increase inthe shear strength for a given volume fraction of particulate. Bydecreasing the size of the particulate, the total mass and volume ofparticulate in the composite need not change. In this manner, valuableproperties of the matrix material are expected to remain constant or beimproved by decreasing the size of the particulate rather than beingaltered or compromised as might occur if the particulate loading wereincreased.

For example, 10 μm powders have a volume of about 5.24×10⁻¹⁰ cc/particle(for spheres), while 100 nm powders have a volume of about 5.24×10⁻¹⁶cc/particle. Everything else remaining same and assuming uniformdistribution, this represents a six order of magnitude difference in thenumber of reinforcing particles in a given volume of the composite. Theincreased dispersant concentration by number significantly decreases theinter-particle spacing (λ). By using 100 nm dispersant particles insteadof 10 micron dispersant particles, the inter-particle spacing (λ) can bereduced by about 100 fold, which translates to a 100 fold enhancement infailure stress, τ.

In order to improve the performance of the metals like copper and alloyslike nickel aluminide, it is preferred that the nanoparticles be fusedon the surface of the metal or alloy powder. This can be accomplishedusing Hosokawa Micron's Mechanochemical Bonding equipment. For example,1 wt % of aluminum oxide nanoparticles can be mechanochemically bondedwith 5 to 20 micron copper powders. Other weight loadings and differentparticle sizes can be utilized as appropriate. The resultingnano-engineered composite particles are ready to be used for oxidedispersion strengthened materials. It is anticipated that the uniformdistribution and the interface bonding of the powders will significantlyenhance the performance of the resulting material.

Alternatively, by using indium tin oxide or conductive nanoparticledispersant, the electrical properties of the resulting oxide dispersionstrengthened alloy can be enhanced. Similarly, by using magneticcompositions, additional functionality can be added to the dispersionstrengthened metal or alloy. In yet other applications, the dispersantcomposition may be chosen to be one that is thermodynamically stablewith the matrix at processing and use temperatures and environments. Toillustrate, but not limit, the use of yttrium aluminum garnet instead ofyttria in aluminum alloys can prevent the degradation of yttriastrengthened aluminum alloy over time at high temperatures due to thereaction thermodynamically favored between yttria and aluminum.

EXAMPLE 2 Superior Performing Plastics

Mineral fillers are commonly used in plastics to lower cost or toenhance performance of the plastic. These mineral fillers are oftennanoscale powders, submicron powders or fine powders (e.g., calciumcarbonates, fumed silicas, carbon black, tale). Everything elseremaining same, the shape, the size, and the concentration of mineralfiller addition determines the performance the filler-filled plastic.However, an outstanding problem has been the ability to homogeneouslydistribute nanostructured or submicron mineral fillers as these fillershave tendencies to agglomerate. Another issue is the bonding of thefiller interface to the polymer. These reasons, in part, have limitedthe commercially achieved performance of filled polymers.

To fully appreciate the relevance of nanotechnology to plastics,consider the constitutive equation for tensile strength of a polymer,σ_(B)˜k(Eγ/a)^(1/2)where,

-   -   k: geometric constant    -   E: Young's modulus of the material    -   γ: fracture energy (not surface energy per unit area to account        for plastic flow)    -   a: length of crack

This equation suggests that the tensile strength of a plastic is, inpart, a function of the length of the naturally occurring cracks in acompounded plastic. As a rule of thumb, for compounded plastic powdersof about 20 to 50 micron size, this naturally occurring crack length isusually between 1 to 10 microns. When a plastic fails, it is oftenbecause of stresses that concentrate around these cracks and grow thecrack. The presence of fillers tends to pin these cracks and providesome limited improvement in the performance of the plastic.

Everything else remaining same, if plastic powders can be size-confinedby a well-bonded mineral filler, the crack length can be confined to adomain size less than the plastic powder size. This can significantlyenhance the tensile strength of the compounded plastic. Other mechanicalproperties can similarly be enhanced.

The superior performing plastic can be achieved as follows. Produceplastic powders of less than 5 microns, preferably less than 1 micron,more preferably 0.5 micron, and most preferably 100 nm in size. Coat(with good interface bonding) or mechano-chemically bond a nanoscalefiller on the surface of this plastic powder by any technique therebyforming coated size-confined plastic powders. Ultimately, the presentinvention is used to produce a product from the coated size-confinedplastic powder.

In another embodiment, a further step can comprise processing the coatedsize-confined plastic powders with additional plastic material to form acompounded plastic powder of a size suitable for injection molding. Suchprocess can include agglomeration with uncoated plastic powders or ballmilling or any other technique, and performed, for example, inpost-processing operation 203 shown in FIG. 2.

Table 1 presents specific data on the benefits of nanoparticle enabledsize-confined plastic powders in contrast with conventional polymers,metals and alloys.

TABLE 1 MECHANICAL PROPERTIES OF MATERIALS Typical Tensile MaterialStrength (Yield, MPa) 20-50 micron Polypropylene 30 with naturallyoccurring crack length = 5 micron Aluminum 103 Brass, Annealed 250Bronze, Annealed 270 Nickel Superalloy 276 Low Carbon Steel 285Stainless Steel 290 Nanoparticle size-confined 95 Polypropylene withcrack length confined to 500 nm Nanoparticle size-confined 212Polypropylene with crack length confined to 100 nm

Table 1 suggests that nanoparticle enabled size confinement can enhancethe tensile strength of a plastic to a level where they may be able tocompete with certain metals and alloys. Size-confined nanocompositeplastics become particularly attractive when the tensile strengthexceeds 75 MPa. Given that plastics can be injection molded and formedby other techniques into net shape parts, this approach cansignificantly reduce the cost of making complex parts while deliveringcompetitive structural performance. Plastics are lighter than metals andthe consequent weight related savings could significantly enhance thesystem wide performance. Such enhanced plastics can be useful inautomobiles, mobile consumer products such as laptops, phones andhand-held computers, architecture, and aircraft).

Additionally, size-confined plastic powders with enhanced mechanicalproperties can also reduce capital, operating, and labor costsassociated with such tasks as post-machining, finishing, and others thatare necessary when complex metal parts are being formed. The consequentreduction in environmental waste and the possibility of recycling orreuse further make such nanotechnology attractive. At the end of theiruseful life, such materials can also be used as precursors to make metalcarbides and other inorganics through pyrolysis and related methods.

EXAMPLE 3 Superior Performing Ceramics, Metals and Alloys

As in example 2, nanoscale fillers can also be used with ceramics,metals and alloys to form superior performing materials. Theconstitutive equation presented in example 2 applies to othercompositions of matter with the modification that many compositions donot experience plastic flow and therefore fracture energy has to bereplaced with surface energy per unit area or other suitable quantity.

The superior performing ceramic or metal or alloy can be achieved asfollows. Produce powders of desired composition of average size lessthan 50 microns, preferably less than 5 micron, more preferably 0.5micron, and most preferably 100 nm in size. Coat (with good interfacebonding) or fuse a nanoscale filler on the surface of this powder by anytechnique thereby forming coated size-confined powders with an averagedomain size of the confinement of less than 5 microns, preferably lessthan 1 micron, more preferably 0.5 micron, and most preferably 100 nm insize. Produce a product from the coated size-confined powder.

In another embodiment, a further step can comprise processing the coatedsize-confined powders with additional material to form a compoundedpowder of a size suitable for injection molding or other processingtechnique. Such process can include agglomeration with uncoated powdersor ball milling or any other technique.

Compared with parts produced using 20+ micron powders of conventionalmetals, alloys, and ceramics, parts produced using size-confinedmaterials prepared by the method outlined above can improve tensilestrengths by greater than 25%. Other mechanical, magnetic, electrical,thermal, optical, and other properties of commonly available materialscan similarly be improved by 25% or more.

Uses

This invention can be utilized to further improve the performance ofknown oxide dispersion strengthened alloys. These alloys areparticularly desirable for engines, lighting parts, medical devices,x-ray imaging systems, cryogenic equipment, automotive parts, medicalimplants, nuclear industry, offshore piping, dental alloys, sportinggoods, parts subject to high temperatures or corrosion, andenvironmental cleaning equipment.

Size-confined materials that can offer significantly improvedperformance are useful in wide range of new applications. Of particularinterest are fuel cell system parts and micro-turbines given theimportance of weight and costs for their wide spread commercialacceptance.

This invention can also be used where dissimilar materials need to bebonded. The filler, in such cases can be prepared with a composition ofthe dissimilar material thereby aiding the bonding process betweenmatrix and the dissimilar material.

Further, this invention can be used to engineer other properties ofmaterials, e.g., magnetic, electrical, electrochemical, optical,chemical, catalytic, and thermal. This can be achieved because of thefact that the bonding of another material on the surface of a submicronor nanoscale powder isolates the core particle. To illustrate but notlimit, by coating magnetically soft nanoscale powders (less than 250 nmaverage size) on magnetically hard micron-scale powders (greater than 1micron but less than 1000 microns), the nanocomposite produced isanticipated to exhibit unusual magnetic performance such as the hardmagnetic domains that are functionally isolated from the other similardomains. Such materials are expected to be particularly useful in datastorage, signal transmission, signal interception, intelligencegathering devices, and power conversion devices.

Similarly, by bonding electrically insulating nanoscale powdercompositions on magnetic micron-scale powders, energy storage capacitycan be increased while reducing losses due to eddy currents. Incontrast, current technology using oxidized coatings to provide suchinsulation are limited to magnetic materials that oxidize readily, andcan not independently control the insulator composition or thickness. Inthis manner, the present invention enables production of novel materialsfor electronic components and electrical and energy devices. It isexpected that these devices and components can significantly reducelosses and/or improve energy efficiency and/or improve size toperformance ratio and/or weight to performance ratios by at least by 5%when compared with equivalent devices and components prepared fromuncoated micron-scale powders.

The use of appropriate composition on the surface can help engineer thesurface contributed electrical properties of the composite particles.The disclosed materials can also be used for enabling electricalconductivity in materials used commercially at cryogenic or hightemperatures or unusual environments or in materials processed at hightemperatures to produce a product where the electrical conductivity isnormally poor. Electrical conductivity can be achieved as follows: (a)provide a powder that meets the thermal, structural, and otherperformance requirements of the product, (b) coat the powder withnanoparticles of an electrically conducting substance such as metal oralloy or defect oxides or nitride or carbide or boride to achieve ananocomposite form disclosed herein, (c) process the nanocompositepowders into a product. This method can enable multifunctionalmaterials, i.e. products that provide structural function and provideone or more additional function. For example, aerospace parts can beproduced with such multifunctional materials in order to providestructural support during routine use and provide a method fornon-destructive testing of the parts' integrity during routinemaintenance tests. If the part integrity is good, it is anticipated thatthe electrical conductivity of the part will not change. However, cracksand other incipient failures would change the electrical properties andtherefore would be an easy way to detect incipient failure before thefailure occurs.

Similarly, the use of appropriate composition on the surface can helpengineer the surface contributed properties of the composite particles.The disclosed materials can also be used for targeted drug delivery andprogrammable drug delivery vehicles. Targeted drug delivery can beachieved as follows: (a) provide a magnetic powder that isphysiologically acceptable, (b) coat the magnetic powder with the drugor a polymer containing the drug or a slow-release formulation of thedrug in a composite particle form disclosed herein, (c) administer thedrug orally, by injection, as skin cream, as fluid drops, using surgicalprocedures, or through inhalation, (d) apply electromagnetic field toconcentrate the drug in the area of interest to deliver the drug in thearea of interest.

Programmable drug delivery can be achieved as follows: (a) provide afine powder, submicron powder or nanoscale powder with electromagneticcharacteristics that is physiologically acceptable, (b) coat the powderwith the drug or a polymer containing the drug or a slow-releaseformulation of the drug into a composite particle form disclosed herein,(c) if the drug diffuses rapidly, add a diffusion barrier coating thatcontrols the diffusion rate to the preferred rate (d) administer thedrug orally, by injection, as skin cream, as fluid drops, using surgicalprocedures, or through inhalation, (e) apply magnetic or electricalfield to concentrate the drug in the area of interest to deliver thedrug in the area of interest, (f) develop a program for preferredadministration of the drug, (g) in accordance with this program, applyan electromagnetic field of sufficient intensity causing theelectromagnetic powders to warm up and thereby thermally inducingincreased drug diffusion and delivery rates. Such drug deliveryprocedures can be combined with blood or other body fluid monitors thatmonitor the administered drug or a resultant marker or a byproduct ofthe drug or a waste product of the drug to provide real time informationto make the drug delivery administration program safer, cost effective,and more physiologically optimal.

Fine powders have numerous applications in industries such as, but notlimiting to biomedical, pharmaceuticals, sensor, electronic, telecom,optics, electrical, photonic, thermal, piezo, magnetic, catalytic andelectrochemical products.

Other embodiments of the invention will be apparent to those skilled inthe art from a consideration of the specification or practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with the true scope and spiritof the invention being indicated by the following claims.

1. A method of forming interface engineered material comprising:selecting a fine powder of a material of first composition; selectingnanoparticles of a second composition different an the firstcomposition; chemically bonding the nanoparticles to the surface of thefine a powders thereby creating a nanocomposite powder with aninterfacial layer on the fine powder surface. said interfacial layer ofthird composition distinct from the first composition and the secondcomposition, and wherein the composition of said interfacial layerresults from the chemical bonding of said nanoparticles of the secondcomposition and the fine powders of the first composition.
 2. The methodof claim 1 further comprising a step wherein the nanocomposite powdersare processed into a finished part.
 3. The method of claim 1 wherein thenanoparticle loading is less than 5% by weight.
 4. The method of claim 1wherein the first composition is selected from the group consisting of:metal, alloy, an ceramic.
 5. The method of claim 1 wherein the secondcomposition is selected from the group consisting of: carbide, nitride,boride, chalcogenide, halide, metal, and alloy.
 6. The method of claim 1wherein the fine powder of first composition is a submicron powder. 7.The method of claim 1 wherein the fine powder of first composition is ananoscale powder.
 8. The method of claim 1 wherein the secondcomposition is an oxide.
 9. A nanocomposite powder comprising finepowders of first composition and nanoparticles of second composition,wherein the nanoparticles are chemically bonded to the fine powdersthere creating a nanocomposite powder with an interfacial layer on thefine powder surface, said interfacial layer of composition distinct fromthe first composition and the second composition, and wherein thecomposition of said interfacial layer results from the chemical bondingof said nanoparticles of the second composition and the fine powders ofthe first composition; and wherein the size-confined nanocompositepowder has an average domain size of less than 5 micron.
 10. A productprepared from the nanocomposite powder of claim
 9. 11. The nanocompositepowder claim 9 wherein the nanocomposite powder comprises at least onemetal.
 12. The nanocomposite powder of claim 9 wherein the nanocompositepowder comprises at least one polymer.
 13. The nanocomposite powder ofclaim 9 wherein the nanocomposite powder comprises at least one ceramic.14. The nanocomposite powder of claim 9 wherein the nanocomposite powdercomprises at least one glass.
 15. The nanocomposite powder of claim 9wherein the nanocomposite powder comprises at least one biologicallyactive substance.
 16. The nanocomposite powder of claim 9 wherein thefine powders are magnetic and the nanoparticles are electricallyinsulating.
 17. The nanocomposite powder of claim 9 wherein thenanoparticles comprise an electrically conducting substance.
 18. Thenanocomposite powder of claim 9 wherein the fine powders are submicronpowders.
 19. The nanocomposite powder claim 9 wherein the fine powdersare nanoparticles.
 20. The nanocomposite powder of claim 9 wherein thenanocomposite powder comprises powder with aspect ratio greater than oneand less than 1,000,000.